不平衡运行工况下并网逆变器的阻抗建模及稳定性分析

摘要

As it is,the grid-connected inverter usually works under the condition of unbalanced grid voltage,unbalanced grid impedance and unbalanced filter inductance.This paper studies impedance modeling and stability analysis of grid-connected inverters under the unbalanced operation conditions.Firstly,under the conditions of unbalanced voltage at the point of common coupling and unbalanced inverter filter inductance,the relationships between the voltage imbalance component,the filter inductance and the harmonic component are derived.Then the output admittance model of the grid-connected inverter in the positive sequence and negative sequence coordinates are developed.Thus the analytical expression of the admittance matrix is obtained,and the characteristics of the positive-sequence,the negative-sequence and the coupling admittances are analyzed. Based on the generalized Nyquist stability criterion and the unbalanced admittance expression of the inverter,the stability analysing criterion of the inverter in the unbalanced situation is given.Finally,experimental results are given to verify the stability criterion.%实际运行中，并网逆变器常工作在电网电压、电网阻抗和逆变器滤波电感均不平衡的复杂工况下。文中研究了在此复杂不平衡工况下并网逆变器的阻抗模型及其和电网互联系统稳定性分析策略。在并网逆变器公共耦合点电压不平衡和逆变器滤波电感不平衡运行工况下，推导了电压不平衡分量及滤波电感不平衡和各谐波分量之间的关系，建立了并网逆变器在正、负序坐标下的输出导纳模型，得出了导纳矩阵的解析表达式，并分析了正、负序及耦合导纳的特性。依据广义奈奎斯特判据和逆变器不平衡导纳表达式，给出并网逆变器在不平衡运行工况下也适用的阻抗稳定性运行判定方法。最后，对不平衡工况下所研究的系统稳定性判据的有效性进行了实验验证。